How to initialize Singleton?

singleton.kt

companion object {
  
  @Volatile
  private var INSTANCE: WordRoomDatabase? = null
  
  fun getDatabase(context: Context): WordRoomDatabase {
    return INSTANCE ?: synchronized(this) {
      val instance = Room.databaseBuilder(context.applicationContext, WordRoomDatabase::class.java, "word_database").build()
      INSTANCE = instance
      // return instance
      instance
    }
  }
}
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private lateinit var INSTANCE: TitleDatabase

fun getDatabase(any_param_you_might_need): return_type {
    synchronized(TitleDatabase::class or this) {
        if (!::INSTANCE.isInitialized) {
            INSTANCE = initialize_here
        }
    }
    return INSTANCE
} 


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public class Solution {

    private volatile static Solution uniqueInstance;

    private Solution() {
      
    }

    @Override
    public String toString() {
        return String.valueOf(solutionHashMap);
    }

    public static Solution getInstance() {
        if (uniqueInstance == null) {
            synchronized (Solution.class) {
                if (uniqueInstance == null) {
                    uniqueInstance = new Solution();
                }
            }
        }
        return uniqueInstance;
    }
}

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    companion object {
        private lateinit var sInstance: StockLiveData

        @MainThread
        fun get(symbol: String): StockLiveData {
            sInstance = if (::sInstance.isInitialized) sInstance else StockLiveData(symbol)
            return sInstance
        }
    }